<Construir dinâmicamente uma gridview mantendo o estado entre postbacks ⁄ >

body{
font-family: Tahoma, Verdana, Arial, sans-serif;font-size: 11px;color: #000;
margin: 8px;text-align: center;
}
 
 
/****** <campos input > ******/
select, input{background-color: #ffffff;font-size: 8pt;border: 1px solid #1b5b7e;padding-left: 1px;}
select:hover, input:hover{color: #000080;background-color: #99CCFF}
select:focus, input:focus{color: #000;background-color:#ffffd4; }
 
input[type="text"]:hover{background: #99CCFF url("images/pencil.png") no-repeat bottom right;}
input[type="text"]:focus{background: #ffffd4 url("images/edit.png") no-repeat bottom right;}
 
input[type="submit"]{background: #ffffff url("images/save.png") no-repeat center right;padding-right: 18px;height: 20px;}
input[type="submit"]:hover{background: #ffffd4 url("images/submit.png") no-repeat center right;padding-right: 18px;height: 20px;}
/****** <campos input /> ******/
 
 
/****** <tabelas> ******/
table{border: solid 1px #1b5b7e; margin: 0 auto;}
th{border: solid 1px #3C7088;color: #fff;font-weight: bold;text-align: center;
background: #3C7088 url("images/bg.gif") repeat-x left center; width: 190px;padding: 2px;
}
td{background: #EFEBE7 url("images/bg2.gif") repeat-x left center;border:solid 1px #1b5b7e;padding: 2px;}
a{color: #000080;text-decoration: underline;}
/****** <tabelas/> ******/

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
/// <summary>
/// Summary description for Field
/// </summary>
public class Field
{
    private string _name;
    private Type _type;
 
	/// <summary>
	/// Método construtor
	/// </summary>
	/// <param name="name">Nome do Campo</param>
	/// <param name="systemType">Tipo do Campo</param>
    public Field(string name, string systemType){
        this._name = name;
        this._type = System.Type.GetType(systemType);
	}
 
    /// <summary>
    /// Obter nome do campo
    /// </summary>
    public string FieldName {get{return this._name;}}
 
    /// <summary>
    /// Obter tipo do campo
    /// </summary>
    public Type FieldType {get{return this._type;}}
}

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
using System.Collections;
 
/// <summary>
/// Summary description for Fields
/// </summary>
public class Fields : IEnumerator, IEnumerable {
 
    private ArrayList _fields=new ArrayList();
    private int _pos=-1;
 
	/// <summary>
	/// Método construtor
	/// </summary>
    public Fields(){	}
 
    /// <summary>
    /// Método construtor (overloading)
    /// </summary>
    /// <param name="field">Objecto Campo</param>
    public Fields(Field field) { this.AddField(field); }
 
    /// <summary>
    /// Adicionar Campo
    /// </summary>
    /// <param name="field"></param>
    public void AddField(Field field) {this._fields.Add(field);}
 
    /// <summary>
    /// Implementar as interfaces: IEnumerator, IEnumerable
    /// Isto faz com que possamos usar o foreach
    /// </summary>
    #region IEnumerator Members
 
    public object Current {get{return this._fields[this._pos];}}
 
    public bool MoveNext() {
        this._pos++;
        return (this._pos < this._fields.Count);
    }
 
    public void Reset() {this._pos =-1;}
 
    #endregion
 
    #region IEnumerable Members
 
    public IEnumerator GetEnumerator() {
        return (IEnumerator)this;
    }
 
    #endregion
}

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
using System.Collections;
 
/// <summary>
/// Class que contém os registos da DataTable
/// </summary>
public class Record{
    private Hashtable _arr = new Hashtable();
 
	/// <summary>
	/// Método construtor
	/// </summary>
    public Record() { }
 
    /// <summary>
    /// Adicionar informação a um campo
    /// </summary>
    /// <param name="col">Campo</param>
    /// <param name="value">Valor</param>
    public void AddFieldValue(string col, string value) {this._arr.Add(col, value);}
 
    /// <summary>
    /// Obter valor de um determinado campo
    /// </summary>
    /// <param name="field">Campo</param>
    /// <returns>Valor do Campo</returns>
    public string GetFieldValue(string field) { return this._arr[field].ToString();}
 
    /// <summary>
    /// Obter o número de colunas do registo
    /// </summary>
    /// <returns></returns>
    public int Count() { return this._arr.Count;}
}

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
using System.Collections;
/// <summary>
/// Class que fornece informações,
/// só possui métodos/atributos estáticos
/// </summary>
public class Settings {
 
    static public string mySessionName = "MyPersistentDataTable";
    static public string[] column_titles = { "BI", "Nome", "Telefone" };
 
    /// <summary>
    /// Obter os nomes das colunas que vão preencher
    /// a DataTable
    /// </summary>
    /// <returns></returns>
    public static Hashtable Columns() {
        Hashtable columns = new Hashtable();
 
        columns.Add(column_titles[0], "System.Int32");
        columns.Add(column_titles[1], "System.String");
        columns.Add(column_titles[2], "System.String");
 
        return columns;
    }
 
    /// <summary>
    /// Método construtor
    /// </summary>
    public Settings() { }
}

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
using System.Collections;
 
/// <summary>
/// Summary description for DynamicGridview
/// </summary>
public class DynamicGridview {
    private DataTable _dt;
    private string _tableName;
    private Int16 _allow_duplicates;
    public enum AllowDuplicates { Yes = 1, No = 0 }
 
    /// <summary>
    /// Método construtor
    /// </summary>
    /// <param name="dataTableName">Nome da DataTable armazenada na sessão</param>
    public DynamicGridview(string dataTableName, AllowDuplicates allow) {
        this._dt = new DataTable(dataTableName);
        this._tableName = dataTableName;
        this._allow_duplicates = (Int16)allow;
    }
 
    /// <summary>
    /// Adicionar colunas à DataTable
    /// </summary>
    /// <param name="col">Colunas</param>
    public void AddColumns(Fields fields) {
        foreach (Field field in fields) {
            this._dt.Columns.Add (new DataColumn(field.FieldName, field.FieldType));
        }
        this.SaveSession();
    }
 
    /// <summary>
    /// Adicionar linha de dados à DataTable
    /// </summary>
    /// <param name="row">Registo</param>
    public void AddRecord(Record record) {
        if (this._allow_duplicates == 0) {
            if (RecordExists(record)) return;
        }
 
        DataRow myNewRow;
        DataColumn auxCol;
 
        myNewRow = this._dt.NewRow();
        int count = this._dt.Columns.Count;
        for (int i = 0; i < count; i++) {
            auxCol = this._dt.Columns[i];
            myNewRow[auxCol] = record.GetFieldValue(auxCol.ColumnName);
        }
 
        this._dt.Rows.Add(myNewRow);
        this.SaveSession();
    }
 
    /// <summary>
    /// Guardar objecto na sessão
    /// </summary>
    public void SaveSession() { HttpContext.Current.Session[this._tableName] = this; }
 
    /// <summary>
    /// Verificar se o registos já se encontra na DataTable
    /// </summary>
    /// <param name="rec"></param>
    /// <returns></returns>
    private Boolean RecordExists(Record rec) {
        if (_dt.Rows.Count == 0) return false;
 
        bool result = false;
        int count = _dt.Columns.Count, aux = 0;
 
        foreach (DataRow row in _dt.Rows) {
            foreach (DataColumn col in _dt.Columns) {
                if (rec.GetFieldValue(col.ColumnName).Equals(row[col.ColumnName].ToString())) aux++;
            }
            if (aux == count) { result = true; break; }
            aux = 0;
        }
        return result;
    }
 
    /// <summary>
    /// Obter DataTable
    /// </summary>
    public DataTable DTable { get { return this._dt; } }
}

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" EnableViewState="false" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>myDynamicGridView</title>
  <link href="style.css" rel="stylesheet" type="text/css" />
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <asp:GridView ID="gridView" runat="server" EnableViewState="false"></asp:GridView>
    <br />
    BI <asp:TextBox ID="txtBI" runat="server"></asp:TextBox>
    &nbsp;Nome <asp:TextBox ID="txtNome" runat="server"></asp:TextBox>
    &nbsp;Telefone <asp:TextBox ID="txtTelefone" runat="server"></asp:TextBox>
    <br /><br /><br />
    <asp:Button ID="btAddRecord" runat="server" OnClick="btAddRecord_Click" Text="Adicionar Registo" />
    <br /><br />
    <asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl="~/other_page.htm">Ir para outra página</asp:HyperLink>
  </div>
  </form>
</body>
</html>

using System;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
using System.Collections;
 
public partial class _Default : System.Web.UI.Page {
 
    DynamicGridview myDynamicGrid;
 
    protected void Page_Load(object sender, EventArgs e) {
 
        //se a DynamicGridview já estiver em sessão
        //construímos a gridview
        if (Session[Settings.mySessionName] != null) {
            myDynamicGrid = (DynamicGridview)Session[Settings.mySessionName];
            gridView.DataSource = this.myDynamicGrid.DTable;
            gridView.DataBind();
        }
 
        //a DynamicGridview não se encontra na sessão nem estamos a fazer um postback
        //vamos então instanciar a DynamicGridview e adicionar-lhe as colunas/campos
        else if (!IsPostBack) {
            myDynamicGrid = new DynamicGridview(Settings.mySessionName, DynamicGridview.AllowDuplicates.No);
 
            //<construir campos da gridview>
            Fields fields = new Fields();
            IDictionaryEnumerator columnsEnum = Settings.Columns().GetEnumerator();
            while (columnsEnum.MoveNext()) {
                fields.AddField(new Field(columnsEnum.Key.ToString(), columnsEnum.Value.ToString()));
            }
            //<construir campos da gridview />
 
            //adicionar campos
            this.myDynamicGrid.AddColumns(fields);
        }
    }
 
    protected void btAddRecord_Click(object sender, EventArgs e) {
        this.myDynamicGrid = (DynamicGridview)Session[Settings.mySessionName]; //obter gridview
 
        //criar um registo
        Record rec = new Record();
        rec.AddFieldValue(Settings.column_titles[0], txtBI.Text);
        rec.AddFieldValue(Settings.column_titles[1], txtNome.Text);
        rec.AddFieldValue(Settings.column_titles[2], txtTelefone.Text);
 
        //adicionar registo
        this.myDynamicGrid.AddRecord(rec);
 
        //actualizar gridview
        gridView.DataSource = this.myDynamicGrid.DTable;
        gridView.DataBind();
    }
}